I'm a little confused on what exactly the "generating server" does in an NDR.
For example, I got the following NDR back when sending to a specific domain:
Diagnostic information for administrators: Generating server: example.foo.com firstname.lastname@example.org #< #5.1.1> #SMTP#
Is the "generating server" the MTA that was the last hop to successfully accept the message and tried to deliver the message at the time of the error? Or is the "generating server" the server that gave back the 5.1.1 error (and did NOT accept the message)?
I also noticed the following:
Reporting-MTA: dns; example.foo.com Final-recipient: RFC822; email@example.com Action: failed Status: 5.1.1 X-Supplementary-Info: < #5.1.1>